This invention relates to a process of purifying raw gas produced by a gasification of solid fuels under superatmospheric pressure by a treatment with gases that contain water vapor and free oxygen and, if desired with other gasifying agents.
The pressure gasification of coal by a treatment with oxygen and water vapor and, if desired, carbon dioxide is known, e.g., from U.S. Pat. No. 3,540,867. In that process, the pressure in the gasifying reactor is in the range of approximately 4-150 bars, preferably 10-80 bars. The known process can be used to gasify various kinds of coal as well as peat, which is suitably charged into the gas producer in the form of peat briquettes.
In the above-mentioned patent, it is also described that the hot raw gas produced by pressure gasification is passed through a scrubber-cooler, in which the gas is directly contacted with warm water. The water is supplied through a normal pipe conduit, which contains no dispersing or spraying means. Roof-shaped internal fixtures are incorporated in the scrubber-cooler to ensure a more uniform distribution of the water throughout the cross-section of the well of the cooler. These internal fixtures do not result in an optimum mixing of water and gas so that at least part of the water can flow through the raw gas in threads heaving a small surface area. For this reason the cleaning action of the scrubber-cooler is often insufficient. Particularly, it is not always ensured that the gas is saturated with water vapor at the temperature at which the gas exits from the scrubber-cooler. In the known scrubber-cooler, part of the dust entrained by the raw gas is not sufficiently cooled. Owing to the resulting more elevated temperatures, these dust particles do not act as condensation nuclei. For this reason the raw gas having this purification stage is not virtually free of dust but contains at least about 1000milligrams solids per standard cubic meter.
This invention seeks to improve the purification of the gas and to scrub the raw gas so intensely with water that its dust content meets the requirements to be fulfilled when the gas is to be used in machines. To this end the solids content of the gas should not exceed 10 mg/standard m.sup.3 and should preferably lie in the range of 1-6 mg/standard m.sup.3.